Sheets of material are often used in a variety of industries and in a variety of ways. These materials can include paper, multi-layer paperboard, and other products manufactured or processed in webs or sheets. As a particular example, long sheets of paper or other materials can be manufactured and collected in reels. These types of products are often subject to various out-of-plane deformations like curl.
Curl of a product is often undesirable. Curling may cause jams in printing or copying devices if the curling occurs when a paper sheet is moistened (such as by inkjet ink) or heated (such as in toner-based printers). Processes that convert paperboard to corrugated cardboard may fail due to incomplete adhesion between fluting and liners when curling occurs. Cartons made from curled board typically have diminished strength. Curl in folding boxboards and packaging for liquids may be desirable, such as when limited curl allows easier insertion and withdrawal of items to and from a package. However, this curl may be desirable only if the axis of curl is suitable and the degree of curl is within limits. The actual amount of curl can typically be measured only in a laboratory.